Process for producing phenol and methyl ethyl ketone   

This application is a national stage filing of International Patent Cooperation Treaty Application No. PCT/EP2007/001210 filed Feb. 8, 2007, which claims priority from U.S. Ser. No. 60/773,147 filed Feb. 14, 2006, the disclosure of which is fully incorporated herein by reference.

The present invention relates to a process for co-producing phenol and methyl ethyl ketone.

Phenol and methyl ethyl ketone are important products in the chemical industry. For example, phenol is useful in the production of phenolic resins, bisphenol A, ε-caprolactam, adipic acid, alkyl phenols, and plasticizers, whereas methyl ethyl ketone can be used as a lacquer, a solvent and for dewaxing of lubricating oils.

The most common route for the production of methyl ethyl ketone is by dehydrogenation of sec-butyl alcohol (SBA), with the alcohol being produced by the acid-catalyzed hydration of butenes. For example, commercial scale SBA manufacture by reaction of butylene with sulfuric acid has been accomplished for many years via gas/liquid extraction.

Currently, the most common route for the production of phenol is the Hock process. This is a three-step process in which the first step involves alkylation of benzene with propylene to produce cumene, followed by oxidation of the cumene to the corresponding hydroperoxide and then cleavage of the hydroperoxide to produce equimolar amounts of phenol and acetone. However, the world demand for phenol is growing more rapidly than that for acetone. In addition, the cost of propylene relative to that for butenes is likely to increase, due to a developing shortage of propylene. Thus, a process that uses butenes instead of propylene as feed and co-produces methyl ethyl ketone rather than acetone may be an attractive alternative route to the production of phenol.

It is known that phenol and methyl ethyl ketone can be co-produced by a variation of the Hock process in which sec-butylbenzene is oxidized to obtain sec-butylbenzene hydroperoxide and the peroxide decomposed to the desired phenol and methyl ethyl ketone. An overview of such a process is described in pages 113-121, 261, and 263 of Process Economics Report No. 22B entitled “Phenol”, published by the Stanford Research Institute in December 1977.

Sec-butylbenzene can be produced by alkylating benzene with n-butenes over an acid catalyst. The chemistry is very similar to ethylbenzene and cumene production. However, as the carbon number of the alkylating agent increases, the number of product isomers also increases. For example, ethylbenzene has one isomer, propylbenzene has two isomers (cumene and n-propylbenzene), and butylbenzene has four isomers (n-, iso-, sec-, and t-butylbenzene). For sec-butylbenzene production, it is important to minimize n-, iso-, t-butylbenzene, and phenylbutenes by-product formation. These by-products, especially iso-butylbenzene, have boiling points very close to sec-butylbenzene and hence are difficult to separate from sec-butylbenzene by distillation (see table below).

Butylbenzene Boiling Point, ° C. t-Butylbenzene 169 i-Butylbenzene 171 s-Butylbenzene 173 n-Butylbenzene 183

Moreover, isobutylbenzene and tert-butylbenzene are known to be inhibitors to the oxidation of sec-butylbenzene to the corresponding hydroperoxide, a necessary next step for the production of methyl ethyl ketone and phenol. Thus, for commercial production, it is critical to maximize the sec-butylbenzene selectivity of the alkylation process.

In addition, although sec-butylbenzene production can be maximized by using a pure n-butene feed, it is desirable to employ more economical butene feeds, such as Raffinate-2. A typical Raffinate-2 contains 0-1% butadiene and 0-5% isobutene. With this increased isobutene in the feed, a higher by-product make is expected, which further increases the importance of the sec-butylbenzene selectivity of the process.

U.S. Pat. No. 4,891,458 discloses a process for the alkylation of an aromatic hydrocarbon which comprises contacting a stoichiometric excess of the aromatic hydrocarbon with a C2 to C4 olefin under at least partial liquid phase conditions and in the presence of a catalyst comprising zeolite beta. In addition, it is known from, for example, U.S. Pat. No. 4,992,606 that MCM-22 is an effective catalyst for alkylation of aromatic compounds, such as benzene, with alkylating agents, such as olefins, having from 1 to 5 carbon atoms over a wide range of temperatures from about 0° C. to about 500° C., preferably from about 50° C. and about 250° C. Similar disclosures are contained in U.S. Pat. Nos. 5,371,310 and 5,557,024 but where the zeolites are MCM-49 and MCM-56 respectively.

In our International Application No. PCT/EP2005/008557, filed Aug. 5, 2005, we have described an integrated process for producing phenol and methyl ethyl ketone, the process comprising (a) contacting a feed comprising benzene and a C4 alkylating agent under alkylation conditions with a catalyst comprising zeolite beta or an MCM-22 family zeolite to produce an alkylation effluent comprising sec-butylbenzene; (b) oxidizing the sec-butylbenzene to produce a hydroperoxide; and then (c) cleaving the hydroperoxide to produce phenol and methyl ethyl ketone. The C4 alkylating agent can be a mixed butene feed, such as Raffinate-1 or Raffinate-2.

According to the present invention, it has now been found that the oxidation of sec-butylbenzene is sensitive not only isobutylbenzene and tert-butylbenzene in the feed, but also to higher (C8+) olefins that tend to be produced as a result of the competing oligomerization reactions that occur when butene is contacted with an acid catalyst under alkylation conditions. It has also been found that the production of these olefin oligomers is increased when a mixed butene feed, such as Raffinate-1 or Raffinate-2, is used as the C4 alkylating agent.

SUMMARY

In one aspect, the present invention resides in a process for producing phenol and methyl ethyl ketone, the process comprising:

(a) contacting benzene and a C4 olefin under alkylation conditions and in the presence of an alkylation catalyst to produce an alkylation effluent comprising sec-butylbenzene and C8+ olefins;

(b) treating said effluent to reduce the amount of said C8+ olefins and produce a treated effluent;

(c) oxidizing the sec-butylbenzene in said treated effluent to produce a hydroperoxide; and

(d) cleaving the hydroperoxide from (c) to produce phenol and methyl ethyl ketone.

Preferably, the treating (b) includes a chemical treatment, such as olefin oligomerization, selective reduction, selective oxidation, esterification, and the addition of heteroatoms to olefins, or a combination thereof.

In one embodiment, the catalyst comprises at least one molecular sieve of the MCM-22 family. Conveniently, the molecular sieve of the MCM-22 family has an X-ray diffraction pattern including d-spacing maxima at 12.4±0.25, 6.9±0.15, 3.57±0.07 and 3.42±0.07 Angstrom. Conveniently, the molecular sieve is selected from MCM-22, PSH-3, SSZ-25, ERB-1, ITQ-1, ITQ-2, MCM-36, MCM-49, MCM-56, UZM-8, and mixtures thereof. Preferably, the molecular sieve is selected from MCM-22, MCM-49, MCM-56 and isotypes thereof.

Preferably, the C4 olefin comprises a linear butene, for example 1-butene and/or 2-butene. In one embodiment, said linear butene is contained in a mixed C4 stream which is subjected to at least one of sulfur removal, nitrogen removal, oxygenate removal, butadiene removal and isobutene removal prior to the contacting (a). Conveniently, said mixed C4 stream is a Raffinate-1 or a Raffinate-2 stream.

Conveniently, said alkylation conditions also include a temperature of from about 60° C. to about 260° C., a pressure of 7000 kPa or less, a feed weight hourly space velocity (WHSV) based on C4 alkylating agent of from about 0.1 to 50 hr−1, and molar ratio of benzene to butene from about 1 to about 50, preferably about 2 to about 10.

In one embodiment, said contacting (a) is conducted under at least partial liquid phase conditions.

In one embodiment, said alkylation effluent produced in (a) comprises polybutylbenzenes and the process further comprises contacting said polybutylbenzenes with benzene in the presence of a transalkylation catalyst to produce sec-butylbenzene. Conveniently, the transalkylation catalyst comprises a molecular sieve selected from zeolite beta, mordenite, USY, MCM-22, PSH-3, SSZ-25, ERB-1, ITQ-1, ITQ-2, MCM-36, MCM-49, MCM-56, UZM-8, and mixtures thereof.

Conveniently, the oxidizing (b) is conducted in the presence of a catalyst, such as a catalyst selected from (i) an oxo (hydroxo) bridged tetranuclear metal complex comprising manganese, (ii) an oxo (hydroxo) bridged tetranuclear metal complex having a mixed metal core, one metal of the core being a divalent metal selected from Zn, Cu, Fe, Co, Ni, Mn and mixtures thereof and another metal being a trivalent metal selected from In, Fe, Mn, Ga, Al and mixtures thereof, (iii) an N-hydroxy substituted cyclic imide either alone or in the presence of a free radical initiator, and (iv) N,N′,N″-trihydroxyisocyanuric acid either alone or in the presence of a free radical initiator. In one embodiment, the oxidization catalyst is a heterogeneous catalyst.

Conveniently, the oxidizing (b) is conducted at a temperature of about 70° C. to about 200° C. and a pressure of about 0.5 to about 20 atmospheres (50 to 2000 kPa). Conveniently, the cleaving (c) is conducted in the presence of a catalyst. The catalyst can be a homogeneous or heterogeneous catalyst. In one embodiment, the catalyst is a homogeneous catalyst, such as sulfuric acid.

Conveniently, the cleaving (c) is conducted at a temperature of about 40° C. to about 120° C., a pressure of about 100 to about 2500 kPa, and a liquid hourly space velocity (LHSV) based on the hydroperoxide of about 0.1 to about 100 hr−1.

In a further aspect, the invention resides in a hydrocarbon composition boiling within 5° C. of sec-butylbenzene and comprising at least 95 wt % sec-butylbenzene and 20 to 1000 ppm wt, preferably 50 to 500 ppm wt, of butene oligomers. Preferably, said composition comprises less than 0.5 wt % of isobutylbenzene and tert-butylbenzene.

As used herein the term C8+ olefin means any olefin containing 8 or more carbon atoms.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a chart comparing the degree of conversion obtained in the oxidation process of Example 6 using a commercially available sec-butylbenzene sample and using the sec-butylbenzene products of Examples 1, 2 (with 2-butene) and 3,4 (with Raffinate-2).

FIG. 2 is a graph comparing the degree of conversion obtained in the oxidation process of Example 7 using a commercially available sec-butylbenzene sample and using the same sample after spiking with various fractions produced by distillation of the butene oligomers obtained in Example 5.

FIG. 3 is a chart comparing the degree of conversion obtained in the oxidation process of Example 12 using a commercially available sec-butylbenzene sample and using the untreated sec-butylbenzene product from Examples 1, 2 (with 2-butene) and 3,4 (with Raffinate-2) and the treated sec-butylbenzene products from Examples 8 to 11.

DETAILED DESCRIPTION

The present invention is directed to a process for producing sec-butylbenzene by alkylating benzene with a C4 alkylating agent, such as a linear butene, and then converting the sec-butylbenzene to phenol and methyl ethyl ketone. The conversion involves initially oxidizing the sec-butylbenzene to produce the corresponding hydroperoxide and then cleaving the resulting hydroperoxide to produce the desired phenol and methyl ethyl ketone. In particular, the invention is based on the discovery that the oxidation step to convert the sec-butylbenzene to the corresponding hydroperoxide is highly sensitive to presence of butene oligomers in the alkylation effluent. Moreover, certain butene oligomers, particularly certain C12 oligomers, have boiling points very close to that of sec-butylbenzene and hence can not be readily separated from alkylation effluent by distillation. Thus the present invention seeks to obviate or reduce this problem by subjecting the alkylation effluent to a treatment, preferably a chemical treatment, to reduce the level of butene oligomers in the effluent, typically to less than 1 wt %, preferably less than 0.7 wt %, and most preferably less than 0.5 wt %.

The benzene employed in the alkylation step to produce sec-butylbenzene can be any commercially available benzene feed, but preferably the benzene has a purity level of at least 99 wt %.

The alkylating agent can be any olefin, particularly any monoolefin, having 4 carbon atoms and preferably is a linear butene, such as butene-1 and/or butene-2. The alkylating agent can also be an olefinic C4 hydrocarbon mixture such as can be obtained by steam cracking of ethane, propane, butane, LPG and light naphthas, catalytic cracking of naphthas and other refinery feedstocks and by conversion of oxygenates, such as methanol, to lower olefins.

For example, the following C4 hydrocarbon mixtures are generally available in any refinery employing steam cracking to produce olefins; a crude steam cracked butene stream, Raffinate-1 (the product of remaining after solvent extraction or hydrogenation to remove butadiene from the crude steam cracked butene stream) and Raffinate-2 (the product remaining after removal of butadiene and isobutene from the crude steam cracked butene stream). Generally, these streams have compositions within the weight ranges indicated in Table A below.

TABLE A Raffinate 1 Raffinate 2 Crude C4 Solvent Hydroge- Solvent Hydroge- Component stream Extraction nation Extraction nation Butadiene 30-85%   0-2%  0-2% 0-1% 0-1% C4acetylenes 0-15%  0-0.5% 0-0.5%  0-0.5%   0-0.5% Butene-1 1-30% 20-50% 50-95%  25-75%  75-95% Butene-2 1-15% 10-30% 0-20% 15-40%  0-20% Isobutene 0-30%  0-55% 0-35% 0-5% 0-5% N-butane 0-10%  0-55% 0-10% 0-55%  0-10% Iso-butane  0-1%  0-1%  0-1% 0-2% 0-2%

Other refinery mixed C4 streams, such as those obtained by catalytic cracking of naphthas and other refinery feedstocks, typically have the following composition:

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